Many people use access terminals, such as cell phones and personal digital assistants (PDAs), to communicate with cellular wireless networks. These access terminals and networks typically communicate with each other over a radio frequency (RF) air interface according to a wireless communication protocol such as Code Division Multiple Access (CDMA), perhaps in conformance with one or more industry specifications such as IS-95 and IS-2000. Wireless networks that operate according to these specifications are often referred to as “1xRTT networks” (or “1x networks” for short), which stands for “Single Carrier Radio Transmission Technology.” These networks typically provide communication services such as voice, Short Message Service (SMS) messaging, and packet-data connectivity.
Recently, service providers have introduced access terminals and wireless networks that communicate using a protocol known as EV-DO, which stands for “Evolution Data Optimized.” EV-DO networks, operating in conformance with industry specification IS-856, provide high rate packet-data service (including Voice over IP (VoIP) service) to access terminals using a combination of time-division multiplexing (TDM) on the forward link (from the network to access terminals) and CDMA technology on the reverse link (from access terminals to the network). Furthermore, some access terminals, known as hybrid access terminals or hybrid wireless access terminals, can communicate with both 1x networks and EV-DO networks.
In a wireless network (also referred to interchangeably as a “wireless access network” or “access network”), a traffic channel assignment (TCA) message is used to notify an access terminal of the traffic channel that is assigned to the access terminal. Thus, when an access terminal requests to connect to an access network, the access network assigns a traffic channel to the access terminal so that the network scheduler sees the access terminal as active and allocates timeslots to the access terminal for its communications. The access network then conveys identifies the traffic channel that is assigned in a traffic channel assignment message.